Chlorine, Swimming Pool Helper, Has a Checkered Past

Chlorine, Swimming Pool Helper, Has a Checkered Past

Over the next few months, chlorine will ensure that countless swimming pools don’t turn into microbe-choked petri dishes. That’s only one of many uses we’ve found for the element. We sprinkle it on our food as table salt — a k a sodium chloride. We pump water through pipes made of polyvinyl chloride. Perchlorate, a combination of chlorine and oxygen atoms, fuels rockets and ignites fireworks.

But in other incarnations, chlorine is a bane of our existence. In World War I, the German army unleashed clouds of chlorine gas and killed or injured thousands of enemy -soldiers. The Hudson River is burdened with cancer-causing dioxins, chlorine-bearing compounds dumped from factories along its banks.